youngbeck



March 10, 1964 K. w. YOUNGBECK 3,124,778

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ATTORNEY March l0, 1964 K. w. YoUNGBEcK 3,124,778

VARIABLE REsIs'roRs Filed Sept. 5, 1961 4 Sheets-Sheet 4 F`\ e.. lo

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ATToRNF-Y United States Patent O 3,124,778 VARIABLE RESISTORS Karl W. Youngbeck, Milwaukee County, Wis., assignor to Globe-Union Inc., Milwaukee, Wis., a corporation of Delaware Filed Sept. 5, 1961, Ser. No. 136,048 f 12 Claims. (Cl. SSS-175) This invention relates to variable resistors of a subminiature type.

The increased use of miniature (e.g. 0.500" X 0.500 X 0.187) variable resistors in electrical applications has resulted in a demand for an easily adjustable, accurate and economical structure which is unaffected by acceleration, shock and vibration.

The primary object of the present invention is to provide a miniature variable resistor having a minimum of parts which can be easily assembled and stacked for multiple mounting.

Another object of the present invention is to provide a variable resistor which is sealed against variations in humidity.

A further object is to provide a miniature variable resistor which is positively located during adjustment.

These objects are accomplished by employing a square shaped metal housing which has a shallow insulated cover in which a wire wound resistance element, the terminal connections, and a center post are mounted. This arrangement permits such elements to be quickly and easily assembled to a housing which has a recess in which a gear wheel is mounted for rotation. When the cover is positioned over the recess the center post and resistance element are interconnected by a single piece resilient contactor mounted to rotate on the center post and secured to the gear wheel. This contactor has a wiping arm which rides on the resistance element and a center leaf which provides a bias for holding the gear wheel in position in the recess. A worm gear is sealed into the housing and is adjustable from outside the housing to rotate the gear wheel and vary the resistance of the resistance member.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the embodiments shown in the drawings in which:

FIG. 1 is a top View with half of the housing removed;

FIG. 2 is a view taken on line 2 2 of FIG. 1 showing the contact assembly;

FIG. 3 is a view taken on line 3 3 of FIG. 2 showing the resistance element and contactor;

FIG. 4 is a View in prospective of the resilient contactor;

FIG. 5 is a top view of a modied variable resistor taken on line 5 5 of FIG. 6;

FIG. 6 is a view taken on line 6 6 of FIG. 5;

FIG. 7 is a view taken on line 7 7 of FIG. 6 showing the terminal connection;

FIG. 8 is a view taken on line 8 8 of FIG. 6 showing the resistance element;

FIG. 9 is a view in prospective of the resilient contactor of this modification; and

FIG. 10 is a schematic circuit diagram of these resistors when used as potentiometers.

Referring to FIGS. l to 4 of the drawings, the variable resistor includes a housing 10 made of a heat dissipating metal, such as aluminum, having attened terminal corner 12 and an internal circular recess 14. The housing is provided with diagonally opposite holes 16 for mounting the resistors either singly or in stacks. A notch 18 is provided in the casing adjacent the flattened corner and has a number of grooves 20 to receive lead wires 3,124,778 Patented Mar. 10, 1964 ICC 22, 24, and 26. The lead wires are held in position in the grooves by a lateral projection 28 on an insulating cover 30 also having grooves 32 complementary to the grooves 20. The cover is seated on a shoulder 34 in the recess and an edge 33 of the recess and notch is crimped over the cover and projection to seal it in place.

A resistance element comprising a core 40 wound with a coiled Wire 42 is positioned within a trough 44 on the inner surface of the cover with lead wires or plug-in terminals 22 and 26 connected to the ends of the coiled wire. An electrically conductive post 50 is mounted in recess 52 in the cover with a plug-in terminal or lead wire 24 electrically connected to the post. Thus the cover also forms the insulative mounting and support for the resistance element, take-oli posts and plug-in terminals or leads. This eliminates excessive parts. The conductive post is electrically connected to the wire wound resistance element through a resilient contactor 56 which is secured to a non-pivotally mounted gear wheel 58 in the recess of the housing by inserting tabs 60 through holes 62 in the gear wheel and bending the tabs over. The contactor has a center leaf 64 which is bent back to form a spring that rides on the end of the center post. It has two spaced arms 64a and 64b which engage the gear wheel and thus provide a bias for holding the gear wheel up in the recess. The outer rirn 46 of the contactor is bent downward forming a contact 66 that slides on the surface of the resistance element.

A worm gear 63 is bottomed in hole 70 in the side of the housing and engages the gear wheel so that the contactor can be rotated on the resistance element. The worm gear is held in the housing against axial displacement by a thermoplastic pin 72 riding in a groove '72a and is sealed in the housing by an O-ring 72b. A leaf spring 74 is inserted into groove 76 on the side of the recess to bias the pivotless mounted gear wheel into non-backlash engagement with the worm gear. This centerless construction lessens the need for close tolerances and thus makes the unit easier to manufacture. The contactor can be turned to any position with respect to the resistance element by merely turning the worm gear. Since the cover and worm gear are sealed in the housing the interior of the resistor will be unaffected by foreign matter thereby prolonging the useful life of the device.

In the variable resistor shown in FIGS. 5 through 9, the housing 11 has a ilattened terminal corner 13 and an internal recess 15 having a center post 17 integral therewith. A notch 19 (see FIG. 7) is provided adjacent the flattened corner and has grooves 21 to receive lead wires 23, 25, and 27. The lead wires are held in position in the grooves by a lateral projection 29 on an insulating cover 31 also having grooves 33 complimentary to the grooves 21. The cover is seated on a shoulder 35 in the recess and an edge portion 37 of both the recess and the notch is crimped over the coverand the lateral projection to seal the cover on the housing.

A resistance element having a core 39 wound with a wire 41 is positioned within a trough 43 in the cover, with lead wires 23 and 27 connected to the ends of wire 41. An electrically conducting post 45 having a domed end 47 is seated in a hole 49 formed in the center of the cover with lead 2S electrically connected to the post. A gear wheel 51 is mounted to rotate on post 17 in the recess and is held in position by a resilient contactor 53.

The contactor has a center lead 55 with slots 57 on either end which are clinched on ears 59 on the gear wheel. The center of the center leaf is bent downward with countersunk hole or bearing 51 positioned to rotate on the domed end of the center post and provides a bias to hold the gear wheel in position. A contact 63 is provided on the underside of the outer rim of the contactor which is bent downward to engage the wire on the resistance element. The contactor thus forms an electrical connection between the center post andthe resistance element.

A worm gear 65 is bottomed in a hole 67 in the housing with the worm gear in engagement with the gear wheel. The outer end of the worm gear has an annular slot 69 in which a silicon rubber O-ring 71 is mounted to seal the worm gear in the housing. The worm gear is held against axial displacement by a thermoplastic pin 73 staked in the body 11 and seated in another annular groove 75 in the Worm gear. The resistor is set by turning the worm gear to rotate the gear wheel until the contactor is moved to the desired position on the resistance element.

In either of the above arrangements, backlash between the gear wheel and the contactor has been eliminated through the direct connection between the wheel and the contactor. The resistor has been simplied by mounting the resistance element and take-off post in an insulated cover plate with the take-olf post also forming the thrust bearing for the one piece contactor. The improved mounting arrangement for the worm wheel insures positive setting of the gear wheel and at the same time seals the interior of the potentiometer from humidity and dust.

Although only a few of the embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modiiications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. A subminiature variable resistor comprising, a metallic heat conducting housing having a recess therein, an insulating cover for closing said recess, a wire wound resistance member mounted in said cover, an electrically conductive member embedded in said cover and electrically insulated from said resistance member, terminal leads for said resistance member and conductive member cannied by said cover, `a gear wheel positioned in said recess, an integral resilient contactor mounted on said wheel and slidably engaging both the resistance member and the conductive member, said contactor biasing the wheel into the recess when the cover is mounted on the housing and means operable externally of said housing for rotating said wheel to vary the position of the contactor on the resistance member.

2. A variable resistor according to claim l wherein said contactor includes a center section apertured to engage the conductive member and bowed to provide a bias for holding said gear wheel in said recess.y

3. A variable resistor according to claim 2 in whichv said center section has a pair of oppositely related arms which engage said gear wheel at two diiTerent points toy said contactor means has a resilient outer portion which slides on said resistance element.

5. A variable resistor according to claim 1 wherein said gear wheel has a centerless mounting and a biasing spring urges it into continual contact with said externally operable means.

6. A variable resistor according to claim l in which said electrically conductive member has a domed end and said resilient contactor has a center bearing section positioned to engage said end, said bearing section biasing the gear wheel into said recess and electrically connecting the conductive member and resistance member.

7. A variable resistor comprising, a metallic housing having an anular opening therein and a second opening tangentially extending across a portion of the annular opening, a gear wheel positioned in said annular opening and projecting into said second opening, means extending into said second opening for rotating said gear wheel, insulating cover means for closing said annular opening, a resistance member, an electrically conductive post member and terminal means for said resistance member and said post member mounted on said cover means, and contactor means electrically interconnecting said post and said resistance member, said contactor means being secured to said gear wheel and pivoted on said post, said contactor means providing a biasing force on said wheel to hold it in position in the opening.

8. A variable resistor according to claim 7 wherein said contactor means comprises a single integral unit having a center leaf spring engaging said post and an outer peripheral contact member engaging said resistance member.

9. A variable resistor according to claim 8 wherein said contactor means includes a number of slots for engaging corresponding projecting portions on said gear wheel.

10. A variable resistor according to claim 6 wherein said bearing section includes a pair of radially extending arms which are bent to engage said gear wheel.

1l. A variable resistor according to claim 8 wherein said center leaf spring is bent back on the integral unit in a position to pivotally engage said post member, said spring biasing the wheel away from the post.

l2. A variable resistor according to claim 1l wherein said leaf spring includes a pair of arms extending outward from the free end of said spring in a position to engage the gear wheel thereby providing three points of force acting on said gear wheel.

References Cited in the tile of this patent UNITED STATES PATENTS 2,446,417 Hastings Aug. 3, 1948 2,632,830 Aust et al. Mar. 24, 1953 42,814,705 Eshelman Nov. 26, 1957 2,866,054 Purdy Dec. 23, 1958 2,880,293 Blanco Mar. 31, 1959 2,974,299 Youngbeck Mar. 7, 1961 

1. A SUBMINIATURE VARIABLE RESISTOR COMPRISING, A METALLIC HEAT CONDUCTING HOUSING HAVING A RECESS THEREIN, AN INSULATING COVER FOR CLOSING SAID RECESS, A WIRE WOUND RESISTANCE MEMBER MOUNTED IN SAID COVER, AN ELECTRICALLY CONDUCTIVE MEMBER EMBEDDED IN SAID COVER AND ELECTRICALLY INSULATED FROM SAID RESISTANCE MEMBER, TERMINAL LEADS FOR SAID RESISTANCE MEMBER AND CONDUCTIVE MEMBER CARRIED BY SAID COVER, A GEAR WHEEL POSITIONED IN SAID RECESS, AN INTEGRAL RESILIENT CONTACTOR MOUNTED ON SAID WHEEL AND SLIDABLY ENGAGING BOTH THE RESISTANCE MEMBER AND THE CONDUCTIVE MEMBER, SAID CONTACTOR BIASING THE WHEEL INTO THE RECESS WHEN THE COVER IS MOUNTED ON THE HOUSING AND MEANS OPERABLE EXTERNALLY OF SAID 